Hydraulic lash adjuster



SePt- 1 1959 E. w. scHElBE HYDRAULIC LAsH ADJUSTER Filed Feb. 1s, 195s Arm/ MEV United States Patent HYDRAULIC LASH ADJUSTER Elias W. Scheibe, Grand Rapids, Mich., assignor to Geueral Motors Corporation, Detroit, Mich., a corporation of Delaware Application February 13, 1958, Serial No. 715,145

8 Claims. (Cl. 12S-90) This invention relates to hydraulic lash adjusters for automatically taking up excess lash in valve operating trains of internal combustion engines and the like, and particularly to such adjusters of the self contained plunger and dashpot type in which the hydraulic fluid is sealed within the assembly with no provision for its replenishment from any external source during operation.

Although many such self contained lash adjusters have been proposed heretofore, a common diiiiculty they sought to overcome was that of obtaining an etiective and long lasting seal for the hydraulic fluid without resort to a substantial increase in cost over similar devices having an external fluid supply. Seals of the positive type, e.g. rubber boots, bellows, etc., have generally proved either too expensive for commercial acceptance or have lacked durability for a satisfactory operating life. On the other hand, other seals of the O-ring or gasket type which have rolling or rubbing contact with the relatively reciprocating surfaces, although cheaper, have lacked dependable sealing action.

I have discovered that by using a dual plunger arrangement wherein one of the plungers forms the dashpot cylinder for the other plunger, an effectively sealed lash adjuster is obtained at little or no increased manufacturing cost over those of the externally fed type. A substantial part of the cost saving realized results from this arrangement permitting use of much larger clearance tits between the sliding surfaces. For example, where heretofore a selected tit between plunger and cylinder members was required, it is possible to manufacture the improved lash adjuster with a sufhciently wide tolerance in the diameter of the sliding parts that interchangeability of iit can be employed during assembly.

In my improved lash adjuster, operating thrust is transmitted to the larger plunger by the fluid supporting it and thence by its contained fluid against the smaller plunger therein in series, there being means for unrestricted flow of the iluid only in the direction into the chamber formed between the two plungers from the larger cross-section chamber in which the larger plunger operates. The respective leakage paths along the slidable plunger surfaces are connected so that during thrust applications the fluid leakage past the smaller plunger from the higher pressure chamber is directed into the lower pressure chamber below the larger plunger. Simple O-ring or gasket type seals may be employed to insure the aforementioned direction of uid flow through the restricted leakage paths during thrust transmission.

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The invention will be better understood from the following description of a specific embodiment, having reference to the drawing wherein:

Figure l is a sectional view through a portion of an internal combustion engine having a valve train incorporating my improved hydraulic lash adjuster.

Figure 2 is an enlarged sectional View similar to Figure l, showing the internal construction of the lash adjuster and associated engine parts in greater detail.

Figure 3 is a fragmentary view similar to Figure 2, showing a modied construction.

Referring now in detail to the drawing, an engine cylinder block and crankcase structure 1 is shown, having a working cylinder 2 for a power piston 3. Closing the upper end of the cylinder 2 is a cylinder head 4 in which is mounted a poppet valve 5 normally held in its closed position (shown) by the usual return spring 6. The lash adjuster 7 of this invention is shown slidably guided in a bore S in the crankcase with its lower end riding on a cam 9 which is rotated in timed relation with the engine. Each lift stroke of the cam is transmitted to the poppet valve 5 via the lash adjuster 7, push rod 10 and valve rocker 1l, the latter being journaled in conventional manner on a shaft l2 mounted above the cylinder head 4.

As seen in Figure 2, the lash adjuster comprises an outer generally cup shaped cylinder 13 having its closed end 13 engaging the cam 9. The side walls of this cylinder slidably receive a hollow plunger in the form of a cup shaped inner cylinder 14 whose end wall 15 cooperates with the outer cylinder end wall 13 in defining a lower iluid chamber 16. The side walls of this inner cylinder 14 likewise slidably support a second plunger 17, shown in the form of an inverted cup shaped cylinder, whose end wall 17 abuts the lower end of the push rod 10. Within the inner cylinder 14, between its end wall 15 and the inner plunger 17 is formed a second chamber 18. A quantity of oil or other hydraulic fluid is contained in the chambers 16 and 18 for transmitting cam lifting thrust between the end walls 13', 15 and 17, respectively, in order to raise the push rod 10 and actuate the poppet valve in its opening direction against the Valve return spring 6. Means providing a one Way passage for substantially unrestricted luid flow from the lower chamber 16 to the upper chamber is shown in the form of a passage 19 through the end wall 15, this passage being closed against return flow by a ballcheck valve 20.

A ball retainer 21 seated on the end wall 15 accommodates sufficient opening movements of the ball 20 for such unrestricted How into the chamber 18, and interposed between this retainer 21 and the end wall 17 of the inner plunger is a resilient means in the form of a coil compression spring 22. This spring additionally serves to bias the inner plunger 17 outwardly of the inner cylinder 14. Such biasing action also acts to move the inner cylinder 14 farther inward of the outer cylinder 13, displacing Huid from the lower chamber 14 through the passage 19 and into the upper chamber 18, and thereby taking up all lash between the cam 9 and the poppet valve 5. Intermediate their ends, the side walls of the inner cylinder 14 are provided with one or more ports 23 whose opposite ends terminate in annular grooves 30 and 31 which are at all times covered by the side walls of cylinder 13 and inner plunger 17, respectively. These ports 23, together with theslidable fit between the plunger 17 and inner cylinder 14 and the slidable fit between the latter and the outer cylinder 13, define a restricted leakage path for escape of iiuid from the upper chamber 18 to the lower chamber 16 when pressure of the fluid in these chambers increases during the cam lift stroke.

Outwardly of the ports 23 the side walls of the inner and outer plungers are provided with external grooves in which are disposed suitable sealing means such as the O-rings 26 and 27. Preferably, these are located substantially distant from the ports 23 in order to extend the length of the leakage pathsfor fluid tending to escape from the chambers 16 and 18.

In the fully extended condition of the lash adjuster (prior toY installation ink the engine between the cam 9:

and push rod the end wall 17 of the inner plunger is retained by a snapiring 24 seated in an internal groove provided therefor adjacent the open endl of the outer cylinder 13, and thel inner cylinder end wall 15 is in abutment, or nearly so, with the end: Wall 13 of the outer cylinder; When installedy in the engine the parts assume their normal operating positions with the spring 22 compressed' substantially as shown.

During operation, as load is applied during the cam lift stroke the fluid pressures in the chambers 16 and 18 increase, the increase being greatest in the upper chamber IStand causing the check valve 20 to close the passage 19. The uid in the chambers thence acts to transmit the thrust between the cam and the push rod for opening the poppet'v valve 5 of the engine against its return spring 6. The higher pressure of the fluid in the upper chamber 18, relative to that in the lower chamber 16, causes such leakage fluid as escapes between the'inner plunger 17 and the inner cylinder 14 to flow upwardly to the ports 23, thence through these ports and downwardly between the slidingfsurfaces of the inner cylinder and the outer cylinder' 13. The O-ring seals 26 and 27 serve in cooperation with the ports 23 to directV this restricted leakage flow from the higher pressure chamber 18 into'the lower pres-V sure chamber 16, rather than outwardly of the lash adjuster. Because of the larger cross-sectional area of the inner cylinder (outer plunger) 14 as compared to that of the inner plunger 1'7, the outer plunger will travel in a direction opposite that of the inner plunger and the fluid Y displaced` by the travel of the inner plunger is compensated for by the travel of the outer plunger. When the load is removed, the spring 22 moves the plungers apart, relieving the pressure in the upper chamber 18, whereupon the check valve 2t)V opens tol allow uid to pass into the upper chamber from the lower chamber. The resulting more rapid upward displacement of the inner plunger relative to the downward displacement of the outer plunger serves to take up whatever lash developed in the engine valve train during the previous cam lift stroke.

The chambers 16 and 18 and all passages of the lash adjuster are preferably completely filled with hydraulic uid, to' the exclusion of air, in order to eliminate the possibility of air mixing with the fluid or becoming trapped in a bubble or pocket below one of the plungers, with resultant noisy operation. The differential displacements of the two plungers enables such exclusion of all air from the operating fiuid, while retaining the advantages of a self-contained lash adjuster in eliminating the need for maintaining an external fluid supply.

Filling of the lash adjuster with fluid may be accomplished by assembling the parts while submerged in the uid to -be used. First the outer cylinder 13 is submerged in:a generally upright position, and when completely filled the inner cylinder 14 with the spring and check valve parts is inserted-into the outer cylinder until their respective end walls 13 and-15 are in abutment. Then, while holding these parts in that position, the inner plunger is filled by submerging it in the fluid and inserted into the inner cylinder 14 a distance just short o f the O-ring 27 4 reaching the open end of the inner cylinder. Then the inner cylinder may be allowed to rise. outwardly of. the outer cylinder while the inner plunger is further inserted sufficiently to permit installation of the snap ring 24 in place.

Figure 3 shows an alternative construction which may he employed in event the aforementioned filling method is not used. In this modification, all parts are the same as that previously described except the end wall 17 of the inner plunger is provided with a drilled hole 28, which after filling of the lash `adjuster is sealed by a suitable plug 29. The provision of this hole 28 serves to vent the interior of the inner plunger during assembly, enabling the inner and outer plungers to be rst pre-assembled as a unit, which may then be inserted into the outer cylinder.

As in the case of the previously described embodiment, the assembling is carried out while the parts are submerged in thefluid to be'used.

It is appreciated that numerous minor changesV in the construction and arrangement of the parts may be made without departing from the spirit and scope of the1invention as hereinafter claimed.

I claim:

l. In a hydraulic-lash adjuster having two cup-shaped members in slidable nesting relation and an external thrust transmitting plunger slidable in the inner of said cupshaped members, a quantity of hydraulic fluid between. the plunger and the closed end of the outer of said members, the inner of said members having a one-way passage accommodating substantially unrestricted flow of said iuid" toward the plunger, and a restricted passage for ow of said fluid in the opposite direction.

2. In a self-contained hydraulic lash adjuster having an outer cylinder closed at one end, an inner cylinder slidable therein and having a one-way passage for flow' of` uid into saidl inner cylinder from the closed end ofsaid" outery cylinder, a quantity of fluid in said cylinders for' transmitting thrust to and from said closed end, a plunger slidable in the inner cylinder and adapted to transmit external thrust to and from said' fluid, and resilient means' biasing the plunger outwardly of the inner cylinder, the slidable fit of said inner cylinder with said plunger' and outer cylinder providingV restricted leakage paths for'fluid flow out of said inner cylinder and into said closed endv of' the outer cylinder, respectively.

3. The invention of' claim 2, wherein said inner cylinder has a side port interconnecting said leakage pathsV inter-V mediatethe ends of said inner cylinder.

4. The invention of claim 3, together with sealing,v

means blocking fluid leakage between said plunger and inner cylinder outwardlyl thereof from said port.

5. The invention of claim 4, together with sealing means blocking fluid leakage between'said cylindersl out-- wardly thereofv from said port.

6. In a hydraulic lash adjuster of the self-containedl fluid type, an outer cup-shaped member having imperforate side and end walls, an inner cup-shaped member having imperforate side and end walls, said inner member having its open end extending axially into the open end of said outer member, an intermediate cup-shapedl member having its side Walls slidably interfltting the side Walls ofsaid inner and outer members and having its end to block fluid flow therethrough from within said intermediate member but openable to accommodate how in the reverse direction, said intermediate member side walls having a port extending therethrough, said port having its opposite ends covered by the side walls of said inner andv outer members, and means sealing the intermediate mem-- ber side walls outwardly thereof from saidport to the-side walls of said inner and outer members.

7. The invention of claim 6, wherein said resilient means is a compression spring interposed between the respective end walls of said inner and intermediate members.

8. In a hydraulic lash adjuster including a cylinder closed at one end to define a first chamber, a hollow plunger slidable in said cylinder and defining a second chamber, a second plunger slidable in said hollow plunger, and a quantity of uid in said chambers for transmitting thrust between said cylinder and hollow plunger and said hollow plunger and second plunger, respectively, means 5 pand said second chamber.

References Cited in the file of this patent UNITED STATES PATENTS Winkler May 15, 1956 2,804,060 Bergmann Aug. 27, 1957 

